This invention pertains to a mechanism for transporting logs in a sawmill along the longitudinal axes of the logs.
A device commonly employed to satisfy longitudinal log transporting requirements is known as a sharp chain. One embodiment of a sharp chain assembly includes an elongate, hollow raceway with an opening, or slot, along its upper length. A continuous-loop drive chain with equally-spaced special log-engaging spiked links is propelled through the raceway by sprocket assemblies at the ends of the raceway. The spiked links have projections which extend upwardly through the raceway slot and impale logs which are guided onto the sharp chain assembly by a lateral feed system. Logs are impacted onto the projections by overhead transverse rollers.
Logs thus engaged are propelled along the conveyor system at the speed of the sharp chain through scanners, chippers, saw mechanisms and the like. Chain links are guided out of the chain raceway and around the drive sprocket at the outfeed end of the assembly, returned to the infeed end, guided around a gear, and returned to the chain raceway. Logs are disengaged from the spiked links and transferred to another device at the outfeed end of the log conveyor system.
One problem with this type of sharp chain conveyor is the tendency for logs to develop tipping or wobbling lateral motion perpendicular to the direction of travel of the conveyor. Such motion is undesirable for several reasons: (1) the spiked links follow the lateral motion and, being the widest part of the sharp chain, can be displaced by these lateral forces sufficiently to make contact with a saw blade while traversing sawing equipment, such contact can severely damage saw blades or the sharp chain and may create a safety hazard to personnel operating the equipment; (2) excessive side-loading leading to premature failure of saw blades could result if the lateral displacement occurred during the sawing phase of the operation; and (3) excessive torque may be exerted on the tie strap links adjacent the displaced spiked link causing chain failures.
Another problem with present enclosed-raceway sharp chain log conveyor systems is debris build-up inside the raceway. This debris may interfere with chain transport and impede lubrication of the chain mechanism.
One prior attempt to avoid these problems was to maintain large tolerances between the sharp chain and the sawing mechanism. This solution avoided the saw blade contact problem but limited the lateral region of potential saw cuts on logs and did not solve the saw blade side loading, chain torque, or debris build-up problems.
Another prior attempt to solve the problems was to utilize a V-shaped track on the top of the chain raceway and spiked links with wear-strip-covered faces conformed to the V-shaped track such that the spiked links were held in the groove by the weight of the log. This method, although partially effective, still permitted some tipping and wobbling of logs.
Yet another previous method of addressing the problem is disclosed in U.S. Pat. No. 3,858,713, issued to Allen in 1975. The Allen patent teaches a precision conveyor chain which is constructed with retaining flanges extending to straddle a chainway. Thus, in the Allen assembly, the inventor has chosen a design in which the chain is external of the guide means. The Allen approach, however effective, would entail a major modification to implement in a log conveyor system having an enclosed chain raceway mechanism.
Accordingly, it is general object of the present invention to provide an internal-raceway log conveyor system in which lateral, tipping motion of the conveyed logs is reduced, thereby stabilizing longitudinal log transport. Specifically, the present invention has the following objects:
(1) to provide a sharp chain lateral stabilizing device adaptable to retrofit existing, enclosed chain raceway systems; PA1 (2) to provide an inexpensive mechanism for stabilizing a sharp chain log conveyor system; PA1 (3) to provide a mechanically-simple method for stabilizing a sharp chain log conveyor system; PA1 (4) to provide a retrofitted sharp chain log conveyor system in which the new components are individually replaceable; PA1 (5) to provide a sharp chain log conveyor system which allows reduced tolerances between the sharp chain and saw blades, thereby increasing the lateral region of potential cuts on logs and maximizing productivity; PA1 (6) to increase safety in a sawmill by reducing the possibility of catastrophic contact between the sharp chain conveyors and saw blades; PA1 (7) to provide a maintenance-free, reliable method for sharp chain lateral stabilization; and PA1 (8) to provide a mechanism for cleaning debris from an enclosed chain raceway.